There are two main types of rehabilitation robots. The first type is an assistive robot that substitutes for lost limb movements. An example is the Manus ARM (assistive robotic manipulator), which is a wheelchair-mounted robotic arm that is controlled using a chin switch or other input device. That process is called telemanipulation and is similar to an astronaut’s controlling a spacecraft’s robot arm from inside the spacecraft’s cockpit. Powered wheelchairs are another example of teleoperated, assistive robots.

The second type of rehabilitation robot is a therapy robot, which is sometimes called a rehabilitator. Research in neuroscience has shown that the brain and spinal cord retain a remarkable ability to adapt, even after injury, through the use of practiced movements. Therapy robots are machines or tools for rehabilitation therapists that allow patients to perform practice movements aided by the robot. The first robot used in that way, MIT-Manus, helped stroke patients to reach across a tabletop if they were unable to perform the task by themselves. Patients who received extra therapy from the robot improved the rate of their arm movement recovery. Another therapy robot, the Lokomat, supports the weight of a person and moves the legs in a walking pattern over a moving treadmill, with the goal of retraining the person to walk after spinal cord injury or stroke.

Limitations in functionality and high costs have restricted the availability of rehabilitation robots. Furthermore, teleoperating a robot arm to pick up a bottle of water and bring it to the mouth is time-consuming and requires an expensive robot. To overcome that problem, engineers have worked to build more intelligence into robot arms on wheelchairs. Making robots understand voice commands, recognize objects, and agilely manipulate objects is an important area of advance in robotics generally. Progress in neuroscience stands to significantly advance the development of rehabilitation robots by enabling the implantation of computer chips directly into the brain so that all a user has to do is “think” a command and the robot will do it. Researchers have shown that monkeys can be trained to move a robotic arm in just that fashion—through thought alone.

The major limiting factor in the development of rehabilitation robots is that researchers do not know what exactly needs to happen in order for the nervous system to adapt to overcome a physical impairment. Hard work by the patient is important, but what should the robot do? Researchers are developing rehabilitation robots that assist in movement, resist movement when it is uncoordinated, or even make movements more uncoordinated in an attempt to trick the nervous system into adapting. Advances have been made in the development of robotic exoskeletons, which are lightweight wearable devices that assist in limb movement. Other types of rehabilitation robots could play a role in assisting the nervous system to regenerate appropriate neural connections following stem cell and other medical treatments.